A101794 Numbers k such that 4*k-1, 8*k-1, 16*k-1 and 32*k-1 are all primes.

45, 90, 675, 885, 3030, 4290, 6870, 13410, 14460, 15855, 17850, 18675, 20625, 21885, 25350, 26820, 26925, 28230, 30525, 30705, 31710, 31785, 33375, 34860, 41685, 41940, 57435, 63420, 63570, 71805, 74025, 78585, 83865, 85230, 93075

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Example

4*45-1 = 179, 8*45-1 = 359, 16*45-1 = 719 and 32*45-1 = 1439 are primes, so 45 is a term.

Mathematica

Select[Range[10^5], And @@ PrimeQ[2^Range[2, 5]*# - 1] &] (* Amiram Eldar, May 13 2024 *)

Prog

(PARI) is(k) = isprime(4*k-1) && isprime(8*k-1) && isprime(16*k-1) && isprime(32*k-1); \\ Amiram Eldar, May 13 2024

Crossrefs

Cf. A002515, A101795, A101796, A101797, A101798.

Subsequence of A005099, A005122 and A101790.

Subsequence: A101994.

Sequence in context: A184540 A115827 A070002 * A124017 A121925 A044183

Adjacent sequences: A101791 A101792 A101793 * A101795 A101796 A101797

Keyword

easy,nonn

Author

Douglas Stones (dssto1(AT)student.monash.edu.au), Dec 16 2004

Status

approved